19
Apr
Neonicotinoid Insecticides Found to Disrupt Insects’ Vision and Flying Ability
(Beyond Pesticides, April 19, 2019) Flying insects exposed to neonicotinoid insecticides or its breakdown products experience visual impairment and difficulty flying, according to a study published in the journal NeuroToxicology by researchers at the University of Saskatchewan, Canada. While at face value these impacts may sound non-lethal, any loss of fitness in the wild can make flying insects an easier meal for their predators. “Our findings suggest that very low doses of the pesticide or its metabolic products can profoundly and negatively affect motion detection systems that flying insects, such as locusts, grasshoppers and bees, need for survival,” said Jack Gray, PhD, an expert in neural control of animal behavior at the University of Saskatchewan.
Researchers used locusts as proxies for other flying insects, as the visual processing in their brains is easy to track in laboratory settings. Moreover, as study co-author Rachel Parkinson notes, “Bees and other flying insects use similar neural mechanisms to process visual motion,” making the implications of this study applicable to a wide range of other airborne insects.
And rather than simply focus on the effects of exposure to a single active ingredient, researchers also studied whether its breakdown products (metabolites) resulted in similar impairment.
Locusts flight and escape behavior were tested in wild tunnels after exposure to the neonicotinoid imidacloprid and its metabolites at levels likely to be found in the wild (10 parts per billion). Insects were exposed to the same levels of the chemicals in order to test visual functioning to looming stimuli, which essentially mimics response to an object entering the locusts’ field of vision.
The results show that exposure significantly impairs how locusts to respond to visual stimuli. Researchers found that roughly an hour following an initial exposure, most of the insects either were unable to fly or flew very poorly, unable to respond to stimuli or avoid objects in their flight path. Interestingly, the impacts were more pronounced when exposed to the breakdown products of the pesticide than the active ingredient itself. After imidacloprid exposure, 40% could still fly and respond to stimulus, 30% flew poorly, and 30% could not fly an hour after treatment. But with its metabolite 5-hydroxy-imidacloprid, 80% could not fly at all while the remaining 20% flew poorly.
Concern has long surrounded neonics for their propensity to remain in the environmental for months or even years after exposure. Now, it appears that even after an active ingredient has broken down, it may still continue to poison animal life. “Although they are found in the environment, and insects can be exposed to them, metabolites are not typically tested for toxicity. Our results suggest they should be,” said Dr. Gray.
Although locusts are sometimes considered a pest, they are an important part of the ecology of many landscapes and many animals’ diets, and there are profound implications if these results signal effects in other flying insects. “The ability to see movement is crucial not only for avoiding predators, but also for maintaining a steady flight path,” said study coauthor Rachel Parkinson.
It is evident now that the pollinator crisis was only the most visible aspect of what has been characterized by the New York Times as a global insect apocalypse. A study published in on German nature preserves in 2017 found that flying insect biomass had declined by 75% over the last three decades. But in areas where care has been taken to remove pesticides and improve habitat, like Amsterdam, data finds that diversity and abundance is increasing.
Work to emulate those efforts in your own community by getting involved in grassroots advocacy. The more folks that contact their elected officials, attend and speak at local council meetings, and promote healthy, pesticide-free habitats, the better chance we will have at reversing the crisis, or at the least create some resilient, chemical free oases that will help species bounce back or repopulate other areas. Learn more about how to get involved through Beyond Pesticides Bee Protective webpage.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: University of Saskatchewan Press Release (via ScienceDaily), NeuroToxicology
